DNA typing of HLA]

Recent advance of molecular biology and genetic engineering has made a profound influence on clinical and laboratory medicine. In this article we will review present aspects of DNA typing of HLA-class II alleles. The HLA system is characterized by its highly genetic polymorphisms. HLA -class I (A, B, C) molecule consists of alpha 1, alpha 2, alpha 3, and beta 2-microglobulin domain, and HLA-class II (DR, DQ, DP) molecule consists of alpha 1, alpha 2, beta 1, and beta 2 domain. Differences of amino acid sequences determining polymorphisms of HLA-class II molecule are located mainly on the beta 1 domain, while alpha 1 chain of DQ molecule is also polymorphic. Polymerase chain reaction (PCR) has enabled us to make great progress in DNA typing of HLA, in place of RFLP (restriction fragment length polymorphisms) analysis. One of the most important and valuable advantages is to make us non-radioisotopic detection method available. There are several methods for the further analysis of products of PCR amplification; 1) dot-blot hybridization, 2) PCR-RFLP, 3) PCR-SSCP (single strand conformation polymorphism), 4) DGGE (denaturing gradient gel electrophoresis), 5) direct sequencing. As for dot-blot hybridization, there are also several methods for detecting hybridization; 1) radioactive detection with 32P - labelled probes, 2) colorimetric reaction and 3) chemiluminescent assay. Newly developed chemiluminescent assay yields as high sensitivity just as radioactive probes. HLA-D and -DP specificities have been typed cytologically by mixed lymphocyte culture (MLC) or primed lymphocyte test (PLT) method. Cytological typing will be replaced by PCR analysis in near future.(ABSTRACT TRUNCATED AT 250 WORDS)